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    <title>Document</title>
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    <script>
      function getSun(a, b, ...arr) {
        console.log(arr); // 使用的时候不需要写...
      }
      getSun(1, 2);
      getSun(1, 2, 3, 4, 5); // (3) [2,4,5]
    </script>
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